Attribute-Based Decryption Device Using Staged Key Masking
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Solution Overview
Problem
Attribute-based encryption schemes face challenges in efficiently decrypting data on devices with low processing speed and small memory capacity, particularly in ensuring security against adaptive-secure attackers, due to complex computations involved in the decryption process.
Innovation Solution
A data decryption device that divides the decryption process into stages, using a common key partly decrypting part, a mask common key acquiring part, a mask removing part, and a data decrypting part, with a randomized secret key and mask common key generated to facilitate efficient decryption on devices with limited capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If attribute-based encryption is used to enable intelligent access control, then decryption accuracy and security are improved, but decryption time and computational complexity increase
Solution Approach 1:
The decryption process is divided into two separate stages: (1) a first decryption process that performs attribute verification and obtains a first decryption result, and (2) a second decryption process that uses the first decryption result to obtain the final decryption result. This segmentation allows complex attribute-based decryption to be broken down into manageable steps, improving both security through multi-stage verification and efficiency by enabling early termination when attributes don't match.
2Adaptability or versatility
If complex pairing operations and secret sharing decoding are performed on terminal equipment, then decryption functionality is complete, but device resource requirements exceed capabilities of low-power devices
Solution Approach 1:
The decryption functionality is segmented into two distinct processes with different computational requirements. The first decryption process handles attribute verification and generates intermediate results, while the second decryption process completes the actual decryption using those intermediates. This allows terminal equipment to perform only the lighter first stage locally, while the more complex second stage can be delegated or optimized, making the system adaptable to devices with limited processing power.
Solution Approach 2:
The first decryption process performs preliminary verification of user attributes against the encrypted data's access policy before committing to full decryption. This preliminary action filters out unauthorized access attempts early, preventing wasteful execution of complex decryption operations on incompatible devices and reducing the computational burden on terminal equipment.
3Productivity
If decryption delegation is implemented to reduce terminal processing load, then decryption speed on low-power devices is improved, but security against adaptive attackers is compromised
Solution Approach 1:
By segmenting decryption into two stages, the patent maintains security against adaptive attackers while enabling decryption delegation. The first decryption process performs critical security verification of user attributes and generates encrypted intermediates that reveal no information about the plaintext or key material. This segmentation allows the computationally intensive second decryption stage to be safely delegated to external servers, improving speed on low-power devices without compromising security, as the delegated portion operates on already-verified and encrypted data.
Data Source
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AI summary
The object is to enhance the security of encrypted data by dividing a decrypting process of an attribute-based encryption scheme into a plurality of stages and executing the decrypting process. A KEM key partly decrypting part 320 generates an r-KEM key mask value 321 including a random number element, by performing a decrypting process for an encrypted KEM key 313 being a common key encrypted using an attribute conditional expression, using an r-user secret key 221 which is obtained by including the random number element into a user secret key generated in accordance with the attribute-based encryption scheme. A random number element removal requesting part 330 requests an IC card 400 to remove the random number element from the r-KEM key mask value 321, and acquires a KEM key mask value 411 from the IC card 400. A mask removing part 340 generates a KEM key 341 using the KEM key mask value 411. A data decrypting part 350 decrypts an encrypted data main body 312 into target data 301 using the KEM key 341.